Molecular, Cellular and Developmental Biology, Department ofhttp://hdl.handle.net/2027.42/78360
Thu, 14 Dec 2017 02:12:16 GMT2017-12-14T02:12:16ZGenetic basis of octanoic acid resistance in drosophila sechellia: functional analysis of a fine-mapped regionhttp://hdl.handle.net/2027.42/113257
Genetic basis of octanoic acid resistance in drosophila sechellia: functional analysis of a fine-mapped region
Lopez, Jose M.A.
Drosophila sechellia is a species of fruit fly endemic to the Seychelles islands, which are located northeast of Madagascar off the coast of Africa. Unlike its generalist sister species D. simulans and D. mauritiana, and their closest relative D. melanogaster, D. sechellia evolved to specialize on a single plant species, Morinda citrifolia. Specialization on M. citrifolia is surprising because the fruit of the plant contains toxic compounds, primarily octanoic acid (OA), that are lethal to all Drosophila species except D. sechellia. Although the ecological and behavioral adaptations to this toxic fruit are known, the genetic basis for the evolutionary changes in OA resistance is not. Prior work showed that a genomic region on chromosome 3R, containing 18 genes, contributes to OA tolerance. To determine which gene(s) in this region might be involved in the evolution of OA resistance, I knocked-down expression of each gene in D. melanogaster with RNA interference (RNAi) (i) ubiquitously throughout development, (ii) during the adult stage, and (iii) within specific tissues in D. melanogaster. RNAi knockdown flies were tested for resistance to OA using the mixed effects Cox regression model. I found that knock-down of three neighboring genes, Osiris 6, Osiris 7, and Osiris 8, increased OA sensitivity. Tissue specific knockdowns, however, showed that decreasing expression of these genes in the fat body and salivary glands increases OA tolerance. I show that both Osi6/7 are highly expressed during the first 24 hours of development and that exposure to different stressors induces expression in adults. Although Osi6/7 have no coding change, RNA-seq data shows derived lower expression of these genes in D. sechellia; Osi8 has two derived coding changes in D. sechellia. This study sheds light on the genetic basis of ecological adaptation to a toxic host within Drosophila, and insect-host specialization more broadly.
Masters thesis
Wed, 16 Sep 2015 00:00:00 GMThttp://hdl.handle.net/2027.42/1132572015-09-16T00:00:00ZMasters Dissertation Thesis: Behavioral Effects of amontillado RNAi Knockdown in the Drosophila melanogaster Circadian Clock Neuron Networkhttp://hdl.handle.net/2027.42/113256
Masters Dissertation Thesis: Behavioral Effects of amontillado RNAi Knockdown in the Drosophila melanogaster Circadian Clock Neuron Network
Esquina, Candi M.
Circadian rhythms are endogenous biological oscillations that are present in microbes, plants, nematodes, and mammals. All animals have an oscillation of approximately 24 hours, though the precise period of these oscillations varies between species. In Drosophila melanogaster, circadian rhythms are coordinated by the circadian clock neuron network (CCNN), which is divided into different classes of clock neurons. Many neuropeptides are synthesized in the CCNN, only some of which have been characterized. Before neuropeptides can become bioactive, their precursors have to go through neuropeptide processing. In Drosophila the enzyme involved in the first step of neuropeptide processing is the Drosophila protein convertase 2 (dPC2), also known as “amontillado.” I have used the GAL4/UAS-RNAi genetic tool to knock down amontillado expression in different groups of neurons in the CCNN to observe the effects on the fruit fly’s circadian rhythm of sleep and activity. Changes in such circadian rhythms in amontillado knockdown flies would reveal the roles that neuropeptides released from subsets of neurons play in their control.
Masters Thesis
Wed, 16 Sep 2015 00:00:00 GMThttp://hdl.handle.net/2027.42/1132562015-09-16T00:00:00ZMüller glia: stem cells for generation and regeneration of retinal neurons in teleost fishhttp://hdl.handle.net/2027.42/102536
Müller glia: stem cells for generation and regeneration of retinal neurons in teleost fish
Lenkowski, Jenny; Raymond, Pamela
Adult zebrafish generate new neurons in the brain and retina throughout life. Growth-related neurogenesis allows a vigorous regenerative response to damage, and fish can regenerate retinal neurons, including photoreceptors, and restore functional vision following photic, chemical, or mechanical destruction of the retina. Müller glial cells in fish function as radial-glial-like neural stem cells. During adult growth, Müller glial nuclei undergo sporadic, asymmetric, self-renewing mitotic divisions in the inner nuclear layer to generate a rod progenitor that migrates along the radial fiber of the Müller glia into the outer nuclear layer, proliferates, and differentiates exclusively into rod photoreceptors. When retinal neurons are destroyed, Müller glia in the immediate vicinity of the damage partially and transiently dedifferentiate, re-express retinal progenitor and stem cell markers, re-enter the cell cycle, undergo interkinetic nuclear migration (characteristic of neuroepithelial cells), and divide once in an asymmetric, self-renewing division to generate a retinal progenitor. This daughter cell proliferates rapidly to form a compact neurogenic cluster surrounding the Müller glia; these multipotent retinal progenitors then migrate along the radial fiber to the appropriate lamina to replace missing retinal neurons. Some aspects of the injury-response in fish Müller glia resemble gliosis as observed in mammals, and mammalian Müller glia exhibit some neurogenic properties, indicative of a latent ability to regenerate retinal neurons. Understanding the specific properties of fish Müller glia that facilitate their robust capacity to generate retinal neurons will inform and inspire new clinical approaches for treating blindness and visual loss with regenerative medicine.
Wed, 08 Jan 2014 00:00:00 GMThttp://hdl.handle.net/2027.42/1025362014-01-08T00:00:00ZPedomorphosis revisited: thyroid hormone receptors are functional in Necturus maculosushttp://hdl.handle.net/2027.42/75694
Pedomorphosis revisited: thyroid hormone receptors are functional in Necturus maculosus
Safi, Rachid; Vlaeminck-Guillem, Virginie; Duffraisse, Marilyne; Seugnet, Isabelle; Plateroti, Michelina; Margotat, Alain; Duterque-Coquillaud, Martine; Crespi, Erica J.; Denver, Robert J.; Demeneix, Barbara; Laudet, Vincent
Heterochrony, a difference in developmental timing, is a central concept in modern evolutionary biology. An example is pedomorphosis, retention of juvenile characteristics in sexually mature adults, a phenomenon largely represented in salamanders. The mudpuppy ( Necturus maculosus ) is an obligate pedomorphic amphibian, never undergoing metamorphosis. Thyroid hormone induces tissue transformation in metamorphosing species and this action is mediated by nuclear thyroid hormone (TH) receptors (TRs). The absence of metamorphosis in Necturus has been attributed to a resistance to TH action as treatment with exogenous TH fails to induce transformation. The failure to metamorphose could be due to the lack of TR expression in target tissues, or to a loss of TR function. Toward understanding the molecular basis for the failure of Necturus tissues to respond to TH, and the ultimate cause for the expression of the obligate pedomorphic life history, we characterized the structure, function, and expression of TR genes in Necturus . Strikingly, we found that Necturus TRΑ and TRΒ genes encode fully functional TR proteins. These TRs bind both DNA and TH and can transactivate target genes in response to TH. Both TRΑ and TRΒ are expressed in various tissues. TH treatment in vivo induced expression in the gill of some but not all genes known to be activated by TH in anuran larvae, caused whole organism metabolic effects, but induced no external morphological changes in adults or larvae. Thus, Necturus possesses fully functional TRs and its tissues are not generally resistant to the actions of TH. Rather, the absence of metamorphosis may be due to the loss of TH-dependent control of key genes required for tissue transformation.
Mon, 01 May 2006 00:00:00 GMThttp://hdl.handle.net/2027.42/756942006-05-01T00:00:00Z